Automatic alternating-current welder



9 I w. R. HARDING 2,023,365

AUTOMATIC ALTERNA'IING CURRENT ELDER Filed Nov. 25, 1933 WITNESS S INVENTOR Patented 3, 1935 UNITED STATES ism-$ AUTOMATIC ALTEBNATINGeUUBBEHT wE nEn William a Harding, momma to Westinghouse Electric 1; Manufacturing Company, East Pittsburgh, Pa in. corporation of Pennsylvania Amman m 1933, serial-No; 699,749

. 7 Claims.

My invention relates generally to arc-welding apparatus and it has particular relation to automatic alternating-current arc-welding appsratus.

The object of my invention, generally stated, is

to provide automaticv arc-welding apparatus which shall be simple and eflicient in operation ance with a variable characteristic of a weldingarc.

Another important object of my invention is to provide for maintaining an alternating-cur rent are between a welding electrode and work and feeding the electrode in accordance with the arc voltage to maintain the arc voltage substantially constant.

Another object of my invention-is to provide for controlling the amount and direction of current flow through the field or armature windings of a series-type motor disposed to feed a welding electrode in accordance with an alternating-current are voltage to maintain the arc voltage substantially constant.

Other objects of my invention will, in part, be obvious and, in part, appear hereinafter.

My invention accordingly is disclosed in the embodiment hereof shown in the accompanying drawing and comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth, the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and'scope of my invention reference may be had to the following detailed description taken in connection with the accompanying drawing, in which the single figure diagrammatically represents a concrete-embodiment of my invention.

Referring now particularly to the drawing, the reference character l0 designates generally a welding transformer having a primary winding H which may be connected to an alternatingcurrent source l2, such as a source having a frequency of 25 or 60 cycles. The transformer Ill is also provided with a secondary winding I3 which is connected to maintain an are H between a welding electrode l5 and work l6 on which a welding operation is to be performed. The welding electrode i5 may either be of the metallic type which is rapidly fused, or it may be of the carbon type which is slowly consumed while the welding operation is being performed.

In'order to feed the welding electrode l5, a motor, shown generally at H, of the alternating-' current series type, is provided having an armature winding l8 and a series field winding l9. As illustrated in the drawing, the armature winding I! may be connected bymeans of a drive shaft to a feed roller 2| which is arranged to cooperate with an idling roller 22 for feeding 10 the welding electrode 15 which is positioned therebetween.

It is desirable to regulate the rate at which the welding electrode I5 is fed by the armature It in such manner that the welding arc l4 may be 15 struck and maintained in order to perform the welding operation. In order to effect this control I have provided for varying the amount ofcurrent flow through both the armature winding I8 and the series field winding 59, as well as for 2 reversing the relative direction of current flow through one of these windings in order to obtain varying speeds and a reversal in the direction of rotation of the armature winding 18. It is well known to those skilled in the art that the arma- 25 ture winding l8 and the field winding l9 should be connected in series circuit relation in order that the flux generated by the field winding ill will be in phase with the current flowing through the armature winding 18. When this relation exists, the motor ll will be enabled to develop the torque necessary to effect its operation and to feed the welding electrode l5 to maintain the are i l.

In order to regulate and reverse the current 5 flow throughone of the windings of the motor H, a regulator, shown generally at 25, is provided which comprises a Wheatstone bridge formed by two parallel circuits, one comprising impedances 28 and 21 connected together at junction-point 40 28, and the other comprising carbon piles 30 and 3|, connected together at junction-point 32. As illustrated in the drawing, the impedance 26 and the carbon pile 30 are connected together at junction-point 33 while the remaining impedance 21 and carbon pile 3| are connected together at junction-point 34.

In the embodiment of the invention illustrated in the drawing and described herein, the series field winding I9 is connected across the bridge 5Q circuit at the junction-points 32 and 28, while the armature winding i8 is connected in series circuit relation with the bridge circuit at the junction-point 33. The remaining terminal of the armature winding 18 and the terminal 34 of has been illustrated as being connected across the bridge circuit and the armature winding I8 has been illustrated as being'connected in series circuit relation with the bridge circuit, it will be readily apparent that the connections of these windings may be interchanged with no change in the functioning of the motor I7. It w ll also be readily apparent that the same relation between the current in the armature winding I8 and the flux generated by the series field winding I9 will be maintained when either connection is used.

Either one or the other of the carbon piles 38 or 3| of the regulator 25 is compressed in order to regulate and reverse the current fiow through the series field winding I9. A relay mechanism, shown generally at'35, is arranged to control the operation of the regulator 25. The relay mechanism 35 may comprise a wedge 36 which may be carried by an armature 31 that is fulcrumed at 38. The wedge 36 is positioned between the ends of the carbon piles 30 and 3|, as illustrated, in order to compress either of them, depending upon the direction of movement of the armature 31. A biasing spring 39, the tension of which may be adjusted by means of a thumb nut 48, is provided for urging the armature 31 in one direction while a winding 4|, connected across the arc I I, to the welding electrode I5 and the work I 5, as shown, is provided for urging the armature 31 in the other direction.

The combination of the carbon piles 30 and 3|- and the relay 35, which is responsive to the voltage of the arc I4, may be constructed into what is known to those skilled in the art as a regulator of the carbon pile type. This regulator may be of the relatively high-speed vibrating type which will maintain an average value of current fiow by governing the degree of compression of the carbon piles 38 and 3| for regulating the speed of the motor I 'I to maintain the desired arc voltage. 1

As illustrated in the drawing, each of the impedances 28 and 21 comprises, respectively, inductors 26a and 21a and resistors 28b and 21b. When the carbon pile 30 is compressed, as when the electrode is fed forwardly, current will flow through the armature winding I8, carbon pile 30, series field winding I9, and impedance 21.. It will be observed that the impedance 26 is connected in parallel circuit relation at this time with the circuit including the series field winding I9 and that a portion of the total current in the armature winding I8 flows through the impedance 26 and does not flow through the series field winding I9.

In order to provide the proper phase relationship between the fiux generated by the series field winding I9 and the current in the armature winding I8, the ratio of resistances of the two beforementioned parallel circuits to their respective inductances is made equal at the point of maximum torque demand. Under this condition, the flux generated by the series field winding I9 and the current in the armature winding I8 will be in phase at the instant when the maximum torque is required. While there may be some shifting of the phase relation between the flux and current when the point of maximum torque demand is departed from, still the phase relation between the flux and current will not be altered to such an extent that proper operation of the motor Il 'may not be maintained.

In like manner, the relation between the inductance and resistance of impedance 21 may be proportioned with respect to the circuit with which it is connected in parallel, when the carbon pile 3| is compressed, so that the same phase relation between the flux generated by the series field winding I9 and the current in the armature winding I8 will be maintained in accordancewith the relation set forth hereinbefore.

Since carbon piles 30 and 3| are inherently non-inductive, there. will be a minimum of phase shift between the currents in the armature winding I8 and the series field winding I9. The degree of compensation required to correct for the phase shift will thus be correspondingly decreased from that requiredif some inductive means were employed to obtain the desired control.

In operation, assuming that the welding electrode I5 is out of engagement with the work I6, a relatively high voltage will exist therebetween. This high voltage will be applied to the winding 4| of the relay 35, which will attract the armature 31 and compress the carbon pile 38, at the same time relieving the compression from the carbon pile 3|. Current will then fiow through the armature winding I8, the carbon pile 30, series field winding I9 and impedance 21. A certain proportion of the current will also flow through the impedance 26.

Under these conditions, the relation between the current fiow in the armature winding I8 and the flux generated by the series field winding I9 will be such as to cause the motor II to feed the welding electrode I5 toward the work I6 until it engages therewith. As soon as the welding electrode I5 engages the work I6, the voltage which is applied to the winding ll of the relay 35 will be reduced to sucha value that the winding 4| will no longer attract the armature 37, and the spring 39 will then cause the compression of the carbon pile 3| through a corresponding movement of the armature 31. At the same time, the compression of the carbon pile 30 willbe relieved. Current will then flow through the armature winding I8, impedance 26, series field winding I9 and carbon pile 3| and a certain proportion of it will flow through the impedance 21.

Under these conditions it will be observed that the current fiowingin the series field winding I9 is reversed with respect to its former direction, while the current flow through the armature windingv I8 is maintained in the same direction. The motor I'I will thereupon reverse and withdraw the welding electrode I5.

It will be readily understood that the with- 5 drawal, of the welding electrode I5 is accompanied by an increase in the voltage which is applied to the winding 4| of the relay 35, and, as a result, the armature 31 will be attracted to relieve the compression on the carbon pile 3| and to apply a compressive force to the carbon pile 30. The current flow-through the series field winding I9 will again be reversed to flow in the original direction as hereinbefore de- The relay 35, in response to departures from substantially .con-.

It will be apparent that the carbon pile 3| may be omitted and in place of it a single set of contacts may be used. Under certain conditions the carbon pile 3i is effective only ln'reversing the direction of rotation of the motor l1, and this action may be brought about at a fixed speed,

' while it is desirable to provide varying speeds in the forward direction to effect moreaecurate control of the arc voltage.

While the foregoing embodiment of my invention has been illustrated and described in connection with an alternating-current source which is used for not only maintaining the welding are but also for effecting the control of the electrode feed motor, it will be readily apparent that a system of control, embodying my invention, may be used in connection with direct-current arc-welding systems in which a direct-current welding arc is maintained and direct current is used for energizing the feed motor. It will also be understood that a current source for the motor I! may be provided that is separate.

from the source l2. However, since in present practice only a single source is used, a corresponding arrangement has been illustrated and described herein.

Since certain further changes may be made in the above construction and different embodiments of the invention may be madewithout departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrativeand not in a limiting sense.

I claim as my invention:

1. Automatic arc-welding apparatus compris ing, in combination, means for feeding a weld-.

ing electrode, a motor including armature and field windings connected to drive said feeding means, a Wheatstone bridge circuit connected in series-circuit relation with one of said windings and to a current source, the remaining winding of said motor being connected across said bridge circuit, and regulating means connected to be responsive to the arc voltage for controlling said bridge circuit to regulate the current flow through said winding connected across the bridge in accordance with changes in the arc voltage.

2. Automatic arc-welding apparatus comprising, in combination, means for feeding a welding electrode, a motor including armature and field windings connected to drive said feeding means, a balancedcircult connected in seriescircuit relation with one of said windings and to a current source, the other of said windings being connected across said balanced circuit, means for controlling said balanced circuit, and regulating means connected to be responsive to a variable characteristic of the welding are for operating said last-named means. a

3. Automatic arc-welding apparatus comprising in combination, means for feeding a welding electrode, a motor including armature andfleld 5 windings connected to drive said feeding means, a balanced circuit connected in series-circuit relation with one of said windings and to a current source, the other of said windings being connected across said balanced circuit, and regum latlng means connected to be responsive to the arc voltage for controlling said balanced circuit.

4. Automatic arc-welding apparatus comprising, in combination, means for feeding a welding electrode, a motor including armature and field windings connected to drive said feeding means,

a non-inductive balanced circuit connected in series-circuit relation with one of said windings, the other of said windings being connected across said balanced circuit, and regulating means connected to be responsive to a variable characteristic of the welding are for controlling said ballanced circuit.

5. Automatic arc-welding apparatus comprising, in combination, electrode-feeding means, a motor provided with armature and field windings and connected to drive said feeding means, a resistor and a carbon pile connected in parallelcircuit relation and in series-circuit relation withone of said windings, the other of said windings beng electrically connected between said resistor and said carbon pile thereby causing the current flow through the other of said windings to vary in accordance with the current flow through said resistor and carbon pile, and control means con-. nected to be responsive tda variable characteristic of the welding are for varying the resistance of said carbon pile.

6. Automatic arc-welding apparatus comprising, in combination, electrode-feeding means, a 0 motor provided with armature and field windings,

" be performed, circuit means for connecting the electrode and work to a current source, a motor as including armature and field windings connected to drive said feeding means, a Wheatstone bridge circuit connected in series-circuit relation with one of said windings and to a source of alternating current, the other of said windings being conso nected across said bridge circuit, one pair of arms of said bridge circuit comprising resistors and the other pair of arms comprising carbon piles, means for compressing either of the carbon piles, to vary the current flow through said other as winding, and regulating means connected to be responsive to a. characteristic of the are for operating said last-named means.

WILLIAM R. HARDING. 

